Heat sink and method for making same

ABSTRACT

A heat sink ( 5 ) for dissipating heat from an electronic component includes a base ( 50 ), and a plurality of fins ( 52 ) formed on the base. The base and the plurality of fins are integrally formed by sintering one or two metallic nano-powders. Since the heat sink is integrally formed by sintering, any thermal resistance between the base and the fins is minimized. In addition, because the base and the fins of the heat sink are all made from one or more metallic nano-powders having good thermal conductivity, a surface area of the heat sink is larger than that of a comparable heat sink made by extrusion. Therefore, a heat transfer efficiency of the heat sink is improved.

TECHNICAL FIELD

The present invention relates to heat sinks and methods for making the same, and more particularly to a heat sink using nanomaterials and a method for making the same.

BACKGROUND

Numerous modern electronic devices, such as computers, comprise electronic components mounted on circuit boards. When the electronic device operates, the electronic components can generate much heat. The heat must be removed from the electronic components; otherwise the electronic device may malfunction or even be damaged or destroyed.

Most electronic components are designed to operate over a wide range of temperatures. If the electronic component operates above its threshold operating temperature, it is liable to operate poorly or improperly. For example, the electronic component may operate too slowly, be less tolerant of voltage variations, be less tolerant of electrical “noise,” or fail prematurely.

One technique for removing heat is to a employ a heat sink assembly in thermal contact with the electronic component. A typical heat sink assembly comprises an aluminum heat sink formed by extrusion. The heat sink comprises a base, and a plurality of fins integrally extending from the base. The process of extrusion necessarily limits the size and surface area of the fins. Therefore, the amount of heat that the heat sink can remove from the electronic component is limited.

In order to overcome the above-described shortcoming, another type of heat sink assembly has been developed. A base and a plurality of fins are separately formed, and are then joined together. There are two main ways to join the fins and the base together. One way is to employ a thermal adhesive, an epoxy resin or the like between the fins, whereby the base and the fins are in effect indirectly joined together. The other way is to employ forging pressing, melting, soldering or the like to in effect directly join the base and the fins together. A typical soldered fin heat sink assembly can be found in U.S. Pat. No. 6,793,011. The heat sink assembly is formed by: placing a sheet or paste of Sn—Zn (tin-zinc) solder upon a copper base plate; placing a folded aluminum fin assembly on the solder sheet or paste; heating the base plate, the folded fin assembly and the solder to a temperature exceeding the liquidus temperature of the solder, and allowing the solder to flow; and cooling the solder to form a soldered joint between the base plate and the folded fin assembly.

However, the soldering process is relatively complicated and time-consuming. In addition, the interposed solder causes thermal resistance between the base plate and the fins. As a result, the heat transfer efficiency of the heat sink assembly is relatively low.

Thus, a new heat sink which overcomes the above-mentioned problems is desired.

BRIEF SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a heat sink which has relatively low thermal resistance between a base and fins thereof.

Another object of the present invention is to provide a heat sink which has improved heat transfer efficiency.

A further object of the present invention is to provide a method for making the above-described heat sink.

To achieve the above-mentioned objects, a heat sink for dissipating heat from an electronic component in accordance with the present invention comprises a base, and a plurality of fins formed on the base. The base and the fins are integrally formed and comprise one or two sintered metallic nano-powders.

In a preferred embodiment, the base and fins are made from a same sintered metallic nano-powder. Alternatively, the base and the fins are made from two different sintered metallic nano-powders. The metallic nano-powder is selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof. A grain size of the metallic nano-powder is in the range from 1 to 99 nanometers. Preferably, the heat sink further comprises nanomaterials such as carbon nanotubes, carbon nanotcapsules. The nanomaterials are attached on a bottom surface of the base, for improving the heat exchange performance of the heat sink.

Further, a method for making the above-described heat sink in accordance with the present invention comprises the following steps: providing a mold having a predetermined shape corresponding to a desired shape of the heat sink, the mold comprising a first portion corresponding to a base of the heat sink and a second portion adjacent the first portion corresponding to a plurality of fins of the heat sink; putting one or two metallic nano-powders in the first and second portions of the mold respectively; and sintering the metallic nano-powders within the mold in an inert gas environment to thereby form the heat sink with the fins integrally formed on the base.

Preferably, the method further comprises the step of forming nanomaterials on the heat sink, for improving the heat exchange performance of the heat sink. For example, forming carbon nanotubes on a bottom surface of the base by chemical vapor deposition. The metallic nano-powders are selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof. A grain size of the metallic nano-powders is in the range from 1 to 99 nanometers.

Since the heat sink of the present invention is integrally formed by sintering, any thermal resistance between the base and the fins is minimized. In addition, because the base and the fins of the heat sink are all made from metallic nano-powders having good thermal conductivity, a surface area of the heat sink is larger than that of a comparable heat sink made by extrusion. Therefore, a heat transfer efficiency of the heat sink is improved.

Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of preferred embodiments of the present invention together with the attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic side view of a heat sink in accordance with a preferred embodiment of the present invention; and

FIG. 2 is a flow chart of a method for making the heat sink of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a heat sink 5 as a heat dissipating device for dissipating heat from an electronic component in accordance with the present invention comprises a base 50, and a plurality of fins 52 formed on the base 50.

The base 50 and the fins 52 are formed integrally by sintering one or two metallic nano-powders. Preferably, the base 50 and the fins 52 are made from a same metallic nano-powder. Alternatively, the base 50 and the plurality of fins 52 are made from different metallic nano-powders. The metallic nano-powder is selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof. A grain size of the metallic nano-powder is preferably in the range from 1 to 99 nanometers. Preferably, the heat sink 5 further comprises nanomaterials such as carbon nanotubes 54 or carbon nanocapsules attached thereon, for improving the heat exchange performance of the heat sink 5. More preferably, the nanomaterials are carbon nanotubes 54, which are formed on a bottom surface 501 of the base 50. The carbon nanotubes 54 are substantially parallel to each other, and substantially perpendicular to the bottom surface 501.

Referring to FIG. 2, a method 6 for making the heat sink 5 in accordance with the present invention comprises the following steps: providing a mold having a predetermined shape corresponding to the heat sink 5, the mold comprising a first portion corresponding to the base 50 and a second portion adjacent the first portion corresponding to the fins 52 (step 60); putting one or two metallic nano-powders in the first and second portions of the mold respectively (step 62); and sintering the metallic nano-powders within the mold in an inert gas environment to thereby form the heat sink 5 with the fins 52 integrally formed on the base 50 (step 64).

Preferably, the base 50 and the fins 52 are made from a same metallic nano-powder, such as aluminum. Alternatively, they can be made from different metallic nano-powders; for example, the base 50 can be made from copper, and the fins 52 can be made from aluminum. Accordingly, in step 62, the same metallic nano-powder may be put in the first portion and the second portion of the mold, or two different metallic nano-powders may be put in the first portion and the second portion of the mold respectively. The metallic nano-powder(s) is (are) selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof. A grain size of the metallic nano-powder(s) is in the range from 1 to 99 nanometers. The inert gas is used to protect the metallic nano-powder(s) from oxidization. Further, the inert gas is one which does not react with the selected metallic nano-powder(s); for example, helium or nitrogen.

Preferably, the method further comprises the step of attaching nanomaterials such as carbon nanotubes 54 or carbon nanocapsules on the heat sink 5, for improving the heat exchange performance of the heat sink 5. In the preferred embodiment, the nanomaterials are carbon nanotubes 54, and the carbon nanotubes 54 are formed on the bottom surface 501 of the base 50. In an alternative embodiment, the carbon nanotubes 54 are formed on the fins 52.

The carbon nanotubes 54 are formed by a chemical vapor deposition method or another suitable method known in the art. A typical chemical vapor deposition method comprises the following steps: forming a catalyst layer on the bottom surface 501 of the base 50, putting the base 50 with the catalyst layer into a reaction chamber, and introducing a carbon source gas into the chamber to contact the catalyst at a predetermined temperature to thereby grow the carbon nanotubes 54 from the bottom surface 501. The carbon nanotubes 54 are substantially parallel to each other, and are substantially perpendicular to the bottom surface 501.

In use of the heat sink 5, the base 50 is attached onto a surface of the electronic component. The carbon nanotubes 54 on the base 50 transfer heat from the electronic component to the base 50 directly and rapidly. This is due to the carbon nanotubes 54 being substantially parallel to the surface of the electronic component, and to the excellent thermal conductivity of the carbon nanotubes 54. The heat is subsequently conducted to the fins 52 of the heat sink 5, and is then dissipated from the fins 52 to ambient air. Because the base 50 and the fins 52 are formed integrally by sintering metallic nano-powders having good thermal conductivity, any thermal resistance between the base 50 and the fins 52 is minimized. In addition, because the base 50 and the fins 52 are made from sintered metallic nano-powder(s), a surface area of the heat sink 5 can be made larger than that of a comparable heat sink made by extrusion. Therefore, a heat transfer efficiency of the heat sink 5 is improved.

It is to be understood that the present invention can be embodied in a variety of other differently configured heat sink assemblies, and is not limited to the embodiment described herein. For example, the present invention can be embodied in a pin fin type of heat sink.

It is also to be understood that, in general, the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. 

1. A heat sink comprising: a base; and a plurality of fins extending from the base; wherein, the base and the fins are integrally formed, and comprise one or more sintered metallic nano-powders.
 2. The heat sink as described in claim 1, wherein the base and the fins are made from a same sintered metallic nano-powder.
 3. The heat sink as described in claim 1, wherein the base and the fins are made from different sintered metallic nano-powders.
 4. The heat sink as described in claim 1, wherein the one or more metallic nano-powders is/are selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof.
 5. The heat sink as described in claim 4, wherein a grain size of the one or more metallic nano-powders is in the range from 1 to 99 nanometers.
 6. The heat sink as described in claim 1, further comprising nanomaterials formed thereon, for improving the heat exchange performance of the heat sink.
 7. The heat sink as described in claim 6, wherein the nanomaterials are carbon nanotubes or carbon nanocapsules.
 8. The heat sink as described in claim 7, wherein the carbon nanotubes are formed on a surface of the base distalmost from the fins.
 9. The heat sink as described in claim 8, wherein the carbon nanotubes are substantially parallel to each other, and are substantially perpendicular to the base.
 10. A method for making a heat sink, comprising the following steps: (a) providing a mold having a predetermined shape according to a desired shape of the heat sink, the mold comprising a first portion corresponding to a base of the heat sink and a second portion adjacent the first portion corresponding to fins of the heat sink; (b) putting one or more metallic nano-powders in the first and second portions of the mold respectively; and (c) sintering the metallic nano-powders within the mold in an inert gas environment to thereby form the heat sink with the fins integrally formed on the base.
 11. The method as described in claim 10, wherein a same metallic nano-powder is put in the first and second portions of the mold.
 12. The method as described in claim 10, wherein the metallic nano-powders put in the first and second portions of the mold are different.
 13. The method as described in claim 10, wherein the one or more metallic nano-powders is/are selected from the group consisting of gold, silver, copper, aluminum, and any alloy thereof.
 14. The method as described in claim 10, wherein a grain size of the one or more metallic nano-powders is in the range from 1 to 99 nanometers.
 15. The method as described in claim 10, further comprising the step of: (d) forming nanomaterials on the heat sink.
 16. The method as described in claim 15, wherein the nanomaterials are formed on the fins.
 17. The method as described in claim 15, wherein the nanomaterials are carbon nanotubes, and the carbon nanotubes are formed on a surface of the base distalmost from the fins.
 18. A method for making a heat dissipating device, comprising the following steps: preparing a mold providing a predetermined shape of said heat dissipating therein; depositing at least one kind of metallic nano-powder within said mold to shape into said heat dissipating device; and sintering said at least one kind of metallic nano-powder within said mold to form said heat dissipating device as a whole.
 19. The method as described in claim 18, wherein said heat dissipating device has a base and fins, and said fins are made of said sintered at least one kind of metallic nano-power and said base is made of another kind of metallic nano-powder.
 20. The method as described in claim 18, further comprising the step of attaching carbon nanotubes to at least one side of said heat dissipating device to enhance heat transmission thereof. 